Home | Transmission | Car Shakes When AC is ON and Idling – {13 Reasons}

Car Shakes When AC is ON and Idling – {13 Reasons}

March 20, 2024 | Victor Lukasso

This article will show you what to do if your car shakes when your AC is turned ON and idling.

When your car shakes when you put on the AC, it implies a more excellent issue that must be addressed. Most people misinterpret the shaky car signs as related to the Air compressor, but it doesn’t always work that way.

The primary function of the Air Conditioner is to provide an excellent interior for car users on a hot day; one of the symptoms of a failed AC isn’t shaking the car.

However, we will discuss other components that work hand in hand with the air compressor and might be responsible for the shaking response whenever the AC is ON and idle.


Car Shakes When AC is ON and Idle – Causes

Excess load on the engine, shaky engine mount, a faulty fuel injector, a bad throttle position sensor, vacuum leak, low engine power, AC idle Speed Compensator, Blocked Condenser Air Flow, old spark plugs, and Overheating Cooling System are the main reasons, why your car vibrates when the AC is turned ON and idle.

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However, a damaged Air compressor can exert excess pressure on the engine when turned on, leading to vibrations.

This doesn’t always happen; the leading cause of vibration is a bad throttle position sensor.

Without wasting much time, let’s discuss the causes of car vibration when the AC is ON in an idle vehicle.

1. Load on Engine

Depending on the number of electronics being powered by the engine, the AC tends to exert a small amount of pressure on the engine’s rotational speed, which often causes issues for manually controlled engines.

However, if the engine load is in excess and you turn on the AC, it’ll likely cause vibration or stalling before it stabilizes.

This occurs because the engine summons the air control motor, which acts as a mini engine when the AC is turned ON.

Also, frequent vibrations and stalling will make other components affiliated with the engine start wearing out.

2. Unstable Engine Mount

The function of an engine mount is to hold the engine and suspension in place despite any force applied to them.

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The engine mount foundation will wear out and lose its grip if the engine has frequent vibrations.

This will increase vibrations and noise from the engine bay whenever the AC is turned ON, even when the car is idle.

3. Bad Throttle Position Sensor

A bad throttle position sensor will shake your car when the AC is on. This is primarily because of its inability to measure how fast the system is operating.

So, when the AC and Revolution per minute (RPMs) aren’t corresponding, there’ll be vibrations.

4. Damaged Spark Plugs

When the spark plug connector is filled with grime, broken, or worn out, they’ll be unable to create a proper connection to turn on the AC.

This will, in turn, cause your car to shake whenever the AC is turned ON in an idle car. You can rectify this by replacing the old spark plugs with new ones.

5. Problematic Fuel Injector

The fuel injector aids fuel supplies to the engine at the correct timing; if the fuel injector can’t do this, the engine won’t perform effectively.

This will cause the engine to stress itself to get the AC to start working, leading to vibrations and shakes.

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You’ll either need to fix your fuel injector or get a replacement.

6. Dirty Throttle Body

7. Loose Hoses

8. Faulty AC Compressor

9. Overheating Cooling System

10. A Vacuum Leak

11. Low Engine Power

If the AC is turned ON when the engine is idling, your car should respond shakily.

This is because air compressors require a certain amount of Horsepower to work, at least 15HP, which will load the idling engine.

This shaky response is to adjust the RPMs and provide sufficient fuel that boosts the engine power.

12. Maladjusted AC Idle Speed Compensator

13. Blocked Condenser Air Flow

Car Shakes When AC Is On and Idle -How to Repair

As discussed above, many factors can shake your car when the AC is turned ON.

If the engine’s excess load causes the problem, try turning off some electrical components before you put on the AC.

Also, if the issue is from a dirty throttle body, you can apply a throttle body cleaner to get it fixed.

In some cases, you’ll be required to change the air compressor. You can also take your car to a mechanic for a proper fix to a shaky car when the AC is turned ON when Idle.

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Meet Victor Lukasso, the owner of V. Auto Basics. Through this blog, Victor Provides Insights on the latest tips, maintenance, repair, and techniques in the automotive world.